I have a customer who is a GM dealer. I asked him about the availability of the new 3/4 ton HDs. He said that dealerships are getting them in, but it is pretty much take what you get. You will not be able to choose one with all the options you want.
On the website they had a "build your own" which would give you a price. I did not check for the new HDs but they had it last year when i bought my Z71. http://www.chevrolet.com